model;
{
   for( i in 1 : n ) {
      x[i] ~ dnorm(21,psi)
   }
   psi ~ dgamma( 0.001,0.001)
   phi <- 1/psi
}

data;
list(n=20,x=c(9,14,15,15,16,18,18,19,19,20,21,22,22,24,24,26,27,29,30,32))

inits;
list(psi=1)